In recent years, liquid crystal display devices have widely been used as flat-panel display devices in many fields. However, significant problems remain, such as significant variation in contrast and coloring depending on the angle of view, difficulty in achieving low power consumption due to the requirement for a light source such as a back light, and limits to the degree of thinness and lightweightness which can be achieved. Another significant problem which remains relates to making liquid crystal display devices flexible.
Accordingly, in recent years there are high hopes for self-illuminating organic EL display devices having organic EL elements as display devices to replace liquid crystal display devices. Organic EL elements are such that organic molecules constituting an organic EL source light up when a current is caused to flow to the organic EL layer, which is sandwiched between an anode and a cathode. An organic EL display device using this organic EL element is self-illuminating and therefore has outstanding thinness, lightweightness, and low power consumption, and moreover has a wide angle of view, and has therefore attracted a great deal of attention as a candidate for a next-generation flat-panel display. Furthermore, such organic EL display devices have the potential to be superior to liquid crystal display devices as relates to flexibility. Indeed, practical implementation of such organic EL display devices has been spreading as a main display for portable music devices and portable telephones, taking advantage of its thinness and wide angle of view.
In general, when organic EL elements are operated for a certain amount of time, light emittance characteristics such as light emittance luminance, uniformity of light emittance, and the like, drop noticeably compared to when first used. Examples of causes of deterioration of such light emittance characteristics include deterioration of an organic layer due to moisture from outside entering an interior of the organic EL element, oxidation of electrodes caused by oxygen in the atmosphere, and separation of the organic layer from the electrodes caused by this moisture or oxygen.
Accordingly, organic EL display devices have been proposed, which are provided with a sealing film for protecting the organic EL element from moisture and oxygen, and sealing material for sealing in the organic EL element. More specifically, for example, an organic EL display device has been proposed which is provided with an element substrate such as a glass substrate, a sealing substrate such as a glass substrate opposing the element substrate, an organic EL element formed on the element substrate and provided between the element substrate and the sealing substrate, a sealing film provided so as to cover the organic EL element in order to protect the organic EL element from moisture and oxygen, and a sealing material that is provided to the sealing film so as to seal the organic EL element and adheres the element substrate and the sealing substrate together (see Patent Document 1, for example).